Global patterns and drivers of phosphorus pools in natural soils 1

15 Abstract. Most phosphorus (P) in soils is unavailable for direct biological uptake as it is locked within primary or secondary 16 mineral particles, adsorbed to mineral surfaces, or immobilized inside of organic material. Deciphering the composition of 17 different P pools in soil is critical for understanding P bioavailability and its underlying dynamics. However, widely used 18 global estimates of different soil P pools are based on a dataset containing few measurements in which many regions or soil 19 types are unrepresented. This poses a major source of uncertainty in assessments that rely on these estimates to quantify soil P 20 constraints on biological activity controlling global food production and terrestrial carbon balance. To address this issue, we 21 consolidated a database of six major soil P pools containing 1857 entries from globally distributed (semi-)natural soils and 11 22 related environmental variables. The P pools (labile inorganic P (Pi), labile organic P (Po), moderately labile Pi, moderately 23 labile Po, primary mineral P, and occluded P) were measured using a sequential P fractionation method. Using the database